president obama paid tribute to nelson mandela today. through his fierce dignity and unbending will to sacrifice his own freedom to others, he transformed south africa and moved all of us. his journey from prisoner to president embodied the promise that human beings and countries can change for the better. his commitment to transfer power and reconcile with those who jailed him set an example for all humanity to aspire to. whether in the lives of nations or in our own personal lives. >>> i promised you the president of the united states, and he's here. let's play "hardball." ♪ >>> it's my honor to introduce the president of the united states. >> hey. >> well, thank you, mr. president. thank you, dr. neil kerwin who is here for having us at the university. >> so what brought you to "hardball"? >> american university. "hardball" was just an excuse to hang out with these fine young people. you know, i've had just wonderful experiences here. first time i spoke here, actually, was when i was running for the presidency and ted kennedy announ